This invention relates to remote liquid level monitoring of propane storage tanks via the public telephone network or other means of telecommunications, like radio frequency; from a remotely located tank to a host computer located at the propane suppliers"" site or to a computer at a centralized location. Such reporting from remote monitors is triggered by previously programmed expected events, or periodically programmed to occur in a timely manner.
The quantity of liquid propane stored and remaining on customer propane tanks should be accurately and frequently measured by the propane dealer to maintain control of his customer""s needs, his [dealer""s] inventory, and control and schedule delivery of propane to his customers. Additionally, the dealer, being responsible for the safety of propane usage by his customers, needs to prevent, as much as possible, his customer from running out of gas. The standard practice for propane dealers to keep track of their customers"" propane consumption is to, whether or not propane is needed, periodically visit each tank and visually read a gauge located on the tank. This industry practice results in a high operating costs and highly inefficient practices.
It is an industry standard that all propane gas suppliers dispatch several route-drivers every day to check the level of propane gas in their tanks for each route, replenishing the tanks should they be low and meet certain criteria. The criteria for refilling low tanks is determined by several factors, including customer""s preference of maximum quantity of propane gas put in the tank each time it is refilled, in order to keep payments low. Also, seasonal changes require changing the frequency and quantities of propane dispensed to each customer. As a consequence, propane suppliers must meet numerous legal requirements and customer demands.
A number of tanks today are fitted with gauges for reading levels in a tank, as well known in the art. A common type of gage is the float gage which has a float that rests on the surface of the fluid being measured. The float is usually connected with other members which move with the float as the fluid level changes. Movement of the float and attached members is sensed by a gage, typically through a magnetic coupling, to provide on-site indication, either visual or otherwise, of the fluid level. A similar system is described in U.S. Pat. No. 5,357,815, incorporated herein by reference, which utilizes a float and a pointer assembly which pivots about an axis in response to the float""s level in a tank to allow for on site inspection of the level in the tank. Other systems have been devised to remotely measure liquid levels in tanks, such as that described in U.S. Pat. No. 4,788,648, incorporated herein by reference, which utilizes differential pressure measurements to calculate the level. Another system is described in U.S. Pat. No. 5,111,201, incorporated herein by reference, which utilizes radio transmissions to transmit level information from a float attached to a potentiometer which varies voltage to correspond to liquid level in a tank. Other representative systems include those described in U.S. Pat. Nos. 5,023,806, 5,265,032, and 5,305,639 each of which is incorporated herein by reference.
Despite the existence of these systems, there is a need in the art for a system which is readily received by and/or retrofitted on to standard tanks which provides an accurate reading that can be transmitted to a host system to accurately monitor the level in a tank.
The present invention comprises a system, methods, and devices to efficiently and remotely monitor a physical condition such as a liquid level of a tank.
The subject system comprises a combination of various electronic modules and mechanical assemblies that interactively will: (1) periodically or continuously sense and monitor one or more physical conditions such as, but not limited to liquid or gas level in a tank, pressure, temperature, flow, displacement, orientation, light (color, intensity, direction), and sound; (2) based on the sensed physical condition, or upon the occurrence of an event, determine what actions to take based on an embedded set of instructions and threshold parameters; (3) transmit appropriate information from a remote site to a host system by one or more means of communications such as, but not limited to radio waves, telephone lines, cable TV circuits, electrical power grid, light signals, sonar signals through water mains, etc.; (4) analyze and make predictive projections based on the information sent and received.
The sensor unit, to sense the level of the liquid in the tank and report it, preferably includes an electronic circuit to decode specific markings on a disc. The disc is magnetically coupled to a master magnet connected to the float within the tank. The master magnet rotates as a function of the level of liquid in the tank. A slave magnet secured to the disc rotates in turn with the master magnet. The disc comprises specifically placed markings to be optically read by appropriate sensors. These markings are preferably located in concentric circles, or tracks, about the disc.
In one embodiment, a plurality of tracks are marked so that the sensors read a binary representation of the angular position of the disc. The marking can be accomplished with dark and light sections, reflective and non-reflective sections, and/or a cut-away section with or without a reflective surface underneath. These contrasting markings provide the binary representations of xe2x80x9conxe2x80x9d and xe2x80x9coffxe2x80x9d or xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d. The markings are preferably arranged such that the binary representations change as the disc rotates according to a Gray-coded scale. Gray-coding is also referred to as xe2x80x9ccyclic binary codexe2x80x9d or reflective code (i.e., a sequence of code values is employed around the disc such that transitions between each Gray-code representation of angular position is accomplished with only a single bit change between each angular position). A sample Gray-coded position indicator is described in U.S. Pat. No. 3,824,587, incorporated herein by reference. This type of coding is preferred for accuracy. For example, as light from a source reflects off a light section, such may represent xe2x80x9c1xe2x80x9d, whereas when light is absorbed by a dark section, such may represent a xe2x80x9c0xe2x80x9d. If, for example, four tracks are utilized to represent position, and the light sections radially overlap on adjacent ends about a 360xc2x0 range (or somewhat less), the binary combinations representing position would include the binary combinations of 0000, 1000, 1100, 0100, 0110, 0011, and 0001. More tracks would provide more combinations as a function of 2(#of tracks), and therefore, a greater accuracy. The number of tracks is a matter of design choice as a function of preferred accuracy. The Gray-scale optically sensed pattern is decoded into a combination of 2 out of 8 audible tones which frequencies are derived as a function of an oscillator frequency and the values listed in FIG. 11, 182, 183.
In addition to the above-noted binary decoded angular representation, greater accuracy can be provided utilizing additional concentric tracks with a colorimetric optically sensed pattern. The pattern preferably utilizes color tracks having variant concentric shading. The tracks may be located anywhere on the disc and, in the example shown in FIG. 4, are presented as a pair of inner concentric tracks. These patterns would provide a greater degree of accuracy, but often the color-sensing devices therefor are more expensive than the binary sensors noted above. The color-coded disc may have light-transmitting or light-reflecting colored information arranged in such a pattern that coded information can be electronically constructed by colorimetric means using an optical sensor or photosensor such as a photodiode, phototransistor, or photocell; and which resolution and accuracy of the positional information increases as a function of the resolution of the color-coded information.
The combination of oscillator frequency and the values listed in FIG. 11, 182, 183. represents the angular position of the color encoded disc. Audible tone function: OSC/Lval=LowFreq tone, OSC/Hval=HighFreq tone. Where OSC is the oscillator frequency driving the frequency generating circuitry and its value can be from 200 KHz to 950 KHz. Even more preferred, the electronic circuit can transmit this information to a receiving/sending unit, either by means of audible tones through a shielded conducting cable or by means of Amplitude Modulation Keyed (AMK) radio frequency waves. The disc can also include only the graduating-scale or colorimetric optically sensed patterns without the binary sensors.
Yet a further embodiment pertains to a method to convert the angular direction of the encoded disc into multi-frequency tones by means of binary coding or colorimetrically measuring the angular direction of an encoded disc by optically analyzing the binary coding and color shades on the disc. The derived level of propane inside the tank is thereby encrypted and transmitted to a receiving/sending unit by means of shielded electrical wires connecting the sensor and receiving/sending units, or by means of wireless radio frequency link between the sensor and receiving/sending unit in the unlicensed RF band by using Carrier-Absent-Carrier-Present RF modulation. This unit may be powered by a stored energy source such as a lithium battery that can last for over 10 years of operation.
The invention further includes various means to enclose the sensor unit of the invention. Preferably, the enclosure provides a recessed top into which the existing gauge being replaced can be sited, thus providing also a means for a visual, on-site indication for the level of liquid propane remaining in the tank. Alternatively, the enclosure does not provide for a visual, on-site indication of the level of liquid propane remaining in the tank.
In a preferred embodiment, the receiving/sending unit comprises a programmable microcontroller-based electronic device linked by RF or by shielded electrical conductors to the sensors. It is connected to the public telephone network in a similar fashion as a regular telephone is connected to the same network; powered from the telephone line while in the active mode and, during its sleep mode, by a lithium battery that can last for over 10 years of operation. This unit is capable of analyzing the information received from the sensor unit and, upon certain events or conditions being met, unobtrusively place a telephone call to a remote host system or to the propane dealer, transmitting the same information or derived data thereof. Preferably, the receiving/sending unit is capable of being reprogrammed remotely by the host system or remote system via a telephone line.
Yet another embodiment of the subject invention pertains to software programs running on a PC type computer, main frame, microcomputer, and the like acting as the host system, which enables the host system to receive, decode, store, interpret and analyze the information sent by the receiving/sending and produce the corresponding information to aid the propane dealer in scheduling and delivering the product.
A further embodiment is directed to a method to reprogram the devices of the subject invention in the field via a connection, such as the Internet, or other similar communication network, that allows the propane dealer to control, set or reset operating parameters and determine events upon which the device will activate, comprising signaling the host system, setting the triggering condition or event; imparting such reprogramming instructions to one or more devices selected based on certain condition(s).
The invention further includes a method to convert tone-pair signals to percentage of tank""s volume filled with liquid propane (FIG. 11), a method to convert tone-pair signals to tank""s level of liquid propane in fractional scale indication, and a method to determine that a particular device is inoperative comprising monitoring calls within a preset or prescheduled periodicity.
A specific aspect of the subject invention pertains to a Propane Tank Colorimetric Level Sensor comprising a hermetically sealed enclosure that can be mounted on top of existing float assemblies of propane tanks and heating oil tanks. This embodiment includes an electronic circuitry to provide a reference source of light in one or more wave lengths, projected onto an encoded disc; an encoded disc such as, but not limited to, a binary coded, a Gray-scale-coded or a color-coded disc (the encoded disc) affixed to a rotating magnet; the means to electronically receive and measure the difference between the various projected and reflected light wave lengths from the encoded disc; the means to convert the amount of light reflected from the encoded disc to frequency (light-to-frequency converter); the means to sense and convert the temperature of the sensor unit to frequency (temperature-to-frequency converter); the means to interconnect to the public telephone network by conventional and FCC approved methods; and the means to send/receive signals and information to/from the remote system.
It is an object of the present invention to improve efficiency and cut costs associated with providing services that involve regular visits to measure and fill storage tanks. The invention allows the dealer to differentiate his service over the prospects current supplier. The dealer is able to offer an enhanced service by offering remote vigilance and fewer visits, all service calls scheduled with adequate notice for the customer and the dealer.
It is another object of the present invention to enable existing dealer outlets to extend their radius of coverage, gaining market share from adjacent markets, by avoiding any unnecessary trip to distant customers, thus turning what would have been a marginal customer to service, into a profitable one.
It is another object of the present invention to generate inventory information on a per-tank level. This information will increase the dealer""s flexibility in timing bulk propane purchases; giving the power to time more efficiently their spot price, forward purchases and/or implement an even more precise hedging program with futures/options contracts, which then facilitates better distribution to branches in order to provide branch operators adequate inventories and to maintain profit margins during changing weather conditions.
One aspect of the invention pertains to an electronic device that replaces the existing gauge on the propane tank and when connected to the customer""s existing telephone line, it can place a toll-free call to a host computer to report a low-gas situation. These calls are answered by a 24-hour automated system, then sorted and transmitted daily (or as the calls are received from the device) via electronic mail to their corresponding dealers, completely unattended. The invention operates unobtrusive of the homeowner, that is, it will not use the telephone line if it is being used, it will try to place a refill call later. This method of providing a low-gas warning allows the dealer ample time to schedule an effective route to dispense his product. The primary benefit for the dealer will be a substantial reduction to his operating costs, because the dealer will then have several days lead time to efficiently dispatch a driver to service only those tanks that called for a refill.
The invention alleviates the inefficient and costly industry practice in which drivers run routes checking more gauges rather than refilling customers tanks.
Further, because the invention can prevent xe2x80x9cout of gas situationsxe2x80x9d, it can be considered a safety device which reduces the hazards that may result when a customer has gas leaks after an out-of-gas situation.
Certain legal requirements may be imposed upon propane gas dealers which are met by the present invention. Liquified Petroleum Gas Laws, Rules and Regulations from every state virtually require the same vigilance from all licensed LP gas dealers. After an out-of-gas occurrence, all LP gas suppliers are required to perform physical inspections and leak checks of gas appliances and gas lines before and after refilling the containers. Further, insurance requirements impose additional obligations upon the LP dealers, making it mandatory that the dealer arrange to have physical access to their customers"" premises in the presence of their customer while inspecting the lines and appliances after an out-of-gas occurrence. In addition, an inactive account for 12 months requires the dealer to initiate appropriate container abandonment procedures, and either remove the container, or perform pressure leak safety checks periodically. In the event the account is reactivated, the supplier must perform a pressure leak safety check prior to filling the container.